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HomeMy WebLinkAboutCUP 2017-0008; OAKMONT OF CARLSBAD; ADDENDUM TO FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE VISIT; 2008-10-30ADDENDUM TO FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING CARLSBAD OAKS NORTH BUSINESS PARK- PHASE I LOT CARLSBAD, CALIFORNIA PREPARED FOR TECHBILT CONSTRUCTION COMPANY SAN DIEGO, CALIFORNIA OCTOBER 30, 2008 PROJECT NO. 06442-32-04A GEOCON INCORPORATED GEOTECHNICAL CONSULTANTS Project No. 06442-32-04A October 30, 2008 Techbilt Construction Company 3575 Kenyon Street San Diego, California 92110 Attention: Mr. Raul Guzman Subject: CARLSBAD OAKS NORTH BUSINESS PARK - PHASE I LOT 1 CARLSBAD, CALIFORNIA ADDENDUM TO FINAL REPORT OF TESTING AND OBSERVATION SERVICES DURING SITE GRADING Reference: 1. Addendum to Final Report of Testing and Observation Services During Site Grading, Carlsbad Oaks North Business Park - Phase 1, Lots 2 and 6, Carlsbad, California, prepared by Geocon Incorporated, dated December 26, 2007 (Project No. 06442-32-04A). Final Report of Testing and Observation Services During Site Grading, Carlsbad Oaks North Business Park - Phase 1, Lots 1 through 9, Carlsbad, California, prepared by Geocon Incorporated, dated August 30, 2006 (Project No. 06442- 32-04A). Grading and Erosion Control Plans for: Carlsbad Oaks North, Phase], Drawing No. 415-9A, C.T. 97-13, prepared by O'Day Consultants, with City of Carlsbad signature dated October 26, 2004. Dear Mr. Guzman: We have prepared this addendum to Reference No. 2 to present information collected during minor grading operations performed on the subject lot subsequent to issuance of the geotechnical report. The additional grading was performed in July 2008. The scope of our services included the following: Observing the grading operation. Performing in-place density and moisture content testing in fill placed and compacted on the subject lot. Performing laboratory testing to aid in evaluating the maximum dry density, optimum moisture content of the compacted fill. Additionally, laboratory testing was performed on samples of soil present at finish grade to evaluate the expansion characteristics and water- soluble sulfate content. 6960 Flanders Drive 0 San Diego, California 92121.2974 0 Telephone (858) 558.6900 0 Fax (858) 558-6159 Revising the As-Graded Geologic Map presented in our report dated August 30, 2006, to reflect the new as-graded conditions. Preparing this addendum report of grading. GRADING As discussed in our report dated August 30, 2006, the initial grading on Lot 1 consisted of removing surficial deposits to expose dense Point Loma Formation. Fills were then placed and compacted within the lot. Where very dense formation soils were exposed at pad sheet-grade, the formation was undercut approximately 5 feet below the design grades presented on the project grading plans (Reference No. 3) and partially replaced with compacted fill. Grading resulted with slope areas and the outer approximately 15 feet of the building pad constructed to design grades. In general, the central portion of the pad was left approximately 2 feet to 4 feet below design sheet-grade upon completion of Phase 1 mass grading. Recent grading consisted of placing and compacting a soil stockpile located in the central portion of the pad. These soils were generated from other areas of the business park and from off-site. Fills were placed in lifts no thicker than would allow for adequate bonding and compaction. The soil was moisture conditioned, as necessary, and mixed during placement. Fills generally consisted of silty to clayey sand to silty sand. The finish elevation contours presented on Figure 1 were provided by the project civil engineer, O'Day Consultants, and reflect actual pad grade after completion of grading. For the following testing references, we utilized the applicable ASTM or California version of the test procedure at the time of testing. During the grading operation, we observed compaction procedures and performed in-place density testing to evaluate the relative compaction of the fill soils. We performed in-place density testing in general conformance with ASTM D 2922. Results of the in-place dry density and moisture content tests pertinent to Lot 1 are summarized on Table I. Lot 1 was initially graded concurrently with the overall Phase 1 mass grading operations for the Carlsbad Oaks North Business Park. Test results for areas beyond Lot 1 are excluded from Table I. Consequently, test number designations are not consecutive. In-place density test results taken during previous and recent grading indicate fill soils have a dry density of at least 90 percent of the laboratory maximum dry density near to slightly above the optimum moisture content at the locations tested. We have revised Figure 1 of Reference No. 2 to include the approximate locations of recent in-place density testing performed on the lot. We performed laboratory testing on samples of soil used for fill to evaluate moisture-density relationships, optimum moisture content and maximum dry density (ASTM D 1557). We also performed laboratory testing on samples collected at fmish grade to evaluate their expansion potential Project to. 06442-32-04A -2 - October 30, 2008 (ASTM D 4829) and water-soluble sulfate content (California Test No. 417). Results of the laboratory tests are summarized on Tables II through IV. Finish Grade Soil Conditions Observations and laboratory test results indicate that randomly sampled soils at finish grade of Lot 1 have an Expansion Index (El) ranging from 46 (low expansive) to 76 (medium expansive). Table 1 presents soil classifications based on ASTM D 4829. Results of the finish grade El tests are summarized on Table ifi. TABLE 1 SOIL CLASSIFICATION BASED ON EXPANSION INDEX ASTM D 4829 Expansion Index (El) Soil Classification 0-20 Very Low 21-50 Low 51-90 Medium 91-130 High Greater Than 130 Very High The building pad of Lot 1 was generally graded to approximately 1- to 3-feet below design pad grade shown in Reference No. 3. Figure 1 reflects the as-graded lot configuration. In general and with respect to design pad grades shown on the project grading plans (Reference No. 3), the upper 10 feet of the pad was graded with soil fill containing rock fragments less than 12 inches in maximum dimension and 6 inches in the upper 3 feet. Rock material greater than 12 inches was placed deeper than 10 feet below the original proposed finish grade. Where an undercut was performed on the pad portion of the lot, the undercut was extended at least 5 feet below the original design sheet grade and replaced with properly compacted fill. The areas that have been undercut are annotated as Quc on the As-Graded Geologic Map. Corrosive Potential Samples obtained for expansion testing were also subjected to water-soluble sulfate testing to assess whether the soil contains high enough sulfate concentrations that could damage normal Portland cement concrete. Table IV summarizes the sulfate test results. In accordance with 2007 California Building Code (CBC), we have classified sulfate test results using guidelines presented in the American Concrete Institute (ACI) 318-08, Building Code Requirements for Structural Concrete and Commentary. The laboratory test results indicate an exposure class Si and S2 with severity medium Project No. 06442-32-04A -- - 3 - October 30, 2008 18 to severe based on Table 4.2.1 of ACI 318-08. ACI guidelines (see Table 4.3.1, ACI 318-08) should be followed in determining the type of concrete to be used. The presence of water-soluble sulfates is not a visually discernible characteristic; therefore, other soil samples from the site could yield different sulfate concentrations. Over time, landscaping activities (i.e., addition of fertilizers and other soil nutrients) may also increase the concentration. Geocon Incorporated does not practice in the field of corrosion engineering. If improvements that could be susceptible to corrosion are planned, it is recommended that further evaluation by a corrosion engineer be performed. SOIL AND GEOLOGIC CONDITIONS Grading on Lot 1 has resulted in compacted fill (Qcf and Quc) overlying the Point Loma Formalion (Kp). A small area of this formation is exposed at grade in the cut slope located along the southwest margin of the lot. The As-Graded Geologic Map (Figure 1) depicts the general geologic conditions observed during grading operations. Geologic contacts should be considered approximate. CONCLUSIONS 1.0 General 1.1 Based on observations and test results, it is the opinion of Geocon Incorporated that the grading, which is the subject of this report, has been performed in substantial conformance with the recommendations of the referenced geotechnical reports. Soil and geologic conditions encountered during grading that differ from those anticipated by the geotechnical report are not uncommon. Where such conditions required a significant modification to the recommendations of the geotechnical report, they have been described herein. 1.2 No soil or geologic conditions were observed during grading that would preclude the continued development of Lot 1. Based upon laboratory test results and field observations, it is our opinion that the fill soils within the subject lot have been compacted to at least 90 percent relative compaction at the locations tested. 1.3 Fine grading and construction of utilities/foundations may encounter very dense formational materials and/or generate some concretionary fragments and/or rock material 12 inches or greater in size. Deeper excavations within the fill (10 feet or greater) for improvements such as utility lines, loading docks, etc., may also encounter oversize material (12 inches or greater). The potential for these conditions should be taken into Project No. 06442-32-04A -4- October 30, 2008 consideration when determining the type of equipment to utilize for future excavation operations. The oversize material may require special handling techniques and exportation. 1.4 It is not uncommon for groundwater or seepage conditions to develop where none previously existed, particularly after landscape irrigation is initiated. The occurrence of induced groundwater seepage from landscaping can be greatly reduced by implementing and monitoring a landscape program that limits irrigation to that sufficient to support the vegetative cover without overwatering. Shallow subdrains may be required in the future if seeps occur after rainy periods or after landscaping is installed. 1.5 References to the thickness and extent of undercutting and rock hold-down areas within the building pads are approximate and were based upon the finish-grade elevations of the approved referenced grading plans. 1.6 Geotechnical recommendations presented in Reference No. 2 remain applicable for the continued development of Lot 1. 1.7 An update geotechnical report presenting fine grading recommendations and geotechnical design criteria for the ultimate development of the lot should be prepared by Geocon Incorporated once free grading plans have been prepared. LIMITATIONS The conclusions and recommendations contained herein apply only to our work with respect to grading and represent conditions at the date of our final observation of grading operations on July 2008. Any subsequent grading should be done in conjunction with our observation and testing services. As used herein, the term observation implies only that we observed .the progress of the work with which we agreed to be involved. Our services did not include the evaluation or identification of the potential presence of hazardous materials. Our conclusions and opinions as to whether the work essentially complies with the job specifications are based on our observations, experience and test results. Due to the inaccuracies inherent in most field and laboratory soil tests, and the necessary assumption that the relatively small soil sample tested is representative • of a significantly larger volume of soil, future tests of the same soil location or condition should not be expected to duplicate specific individual test results of this report. Subsurface conditions, and the accuracy of tests used to measure such conditions, can vary greatly at any time. We make no warranty, express or implied, except that our services were performed in accordance with engineering principles generally accepted at this time and location. Project No. 06442-32-04A - 5 - October 30, 2008 We will accept no responsibility for any subsequent changes made to the site by others, by the uncontrolled action of water, or by the failure of others to properly repair damages caused by the uncontrolled action of water. It is the responsibility of the owner to ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project, are incorporated into the plans, and that the necessary steps are taken to see that the contractor and subcontractors carry out such recommendations in the field. Recommendations that pertain to the future maintenance and care for the property should be brought to the attention of future owners of the property or portions thereof. The findings and recommendations of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and should not be relied upon after a period of three years. If there are any questions regarding this report or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON INCORPORATED Eili111öAWarado RCE 66915 EA:DBE:dmc PLVdq r "n No. 6691 0 r Exp.09!30110 )rn J* OF /Dvt David B. Evans CEO 1860 VIAL DAVID S. Ir No. 18W - CERTIFIED * ENGINEERING GEOI.OGIST \i OF cA'V (6) Addressee (3/del) Techbilt Construction Incorporated Job Site Attention: Mr. Fran Richmond Project No. 06442-32-04A -6- October 30, 2008 TABLE! SUMMARY OF FIELD DENSITY TEST RESULTS Elev. Plus Field Field Field Req'd. or 3/4 Dry Moist. Rd. Rel. Depth Curve Rock Dens. Cont. Comp. Comp. Test No. Date Location (ft) No. (%) (pcI) (%) (%) (%) 8 07/14/05 Lot 1 230 1 0 116.3 9.7 90 90 9 07114105 Lot l 232 1 0 118.5 10.1 92 90 10 07/14/05 Lot 1 236 1 0 117.6 10.0 91 90 11 07/14/05 Lot! 240 1 0 116.7 9.8 90 90 12 07/15/05 Lot 1 238 1 0 119.1 10.4 92 90 13 07/15/05 Lot! 242 1 0 117.1 9.3 91 90 14 07/15/05 Lot 1 244 1 0 116.3 9.5 90 90 15 07/15/05 Lot! 245 1 0 116.8 10.7 91 90 19 07/20/05 Lot! 236 3 0 116.0 9.3 91 90 20 07/20/05 Lot 1 244 - 3 0 115.2 9.5 90 90 21 07/20/05 Lot! 246 3 0 118.0 9.6 92 90 57 07/28/05 Lot 1 255 3 0 117.4 9.6 92 90 58 07/28/05 Lot! 249 3 0 115.2 9.9 90 90 100 08/10/05 Lot! 255 3 0 115.5 11.3 90 90 101 08/10105 Lot! 259 3 0 117.5 10.2 92 90 125 08/17/05 Lot 1 245 4 0 112.3 15.5 91 90 126 08/17/05 Lot 247 4 0 111.6 16.0 90 90 ST 133 08/18/05 Lot 1 250 2 0 119.6 8.9 92 90 ST 134 08/18/05 Lot 1 250 2 0 121.0 9.0 93 90 151 08/23/05 Lot! 252 4 0 114.1 12.5 92 90 ST 158 08/24/05 Lot 1 243 1 0 117:1 8.2 91 90 ST 159 08/24/05 Lot 1 240 1 0 116.3 8.0 90 90 FG 184 08/29/05 Lot 1 260 1 0 117.4 7.2 91 90 FG 185 08/29/05 Lot! 263 1 0 116.8 7.0 91 90 562 03/02/06 Lot! 255 13 0 109.8 12.5 90 90 563 03/02/06 Lot! 256 13 0 111.3 13.0 91 90 564 03/06/06 Lot 1 250 15 0 101.3 20.1 90 90 565 03/06/06 Lot! 258 15 0 103.4 22.1 92 90 566 03/06/06 Lot 1 252 15 0 103.7 19.8 92 90 567 03/06/06 Lot 1 255 15 0 101.9 21.7 91 90 568 03/07/06 Lot 1 251 15 0 103.3 22.0 92 90 569 03/16/06 Lot 1 255 19 0 103.0 10.4 88 90 569 A 03/16/06 Lot 1 255 19 0 105.3 14.8 90 90 570 03/16/06 Lot 1 252 19 0 104.3 11.1 89 90 570A 03/16/06 Lot 1 252 19 0 105.6 14.9 90 90 573 03/28/06 Lot! 253 12 0 116.1 11.8 90 90 574 03/28/06 Lot 1 254 12 0 121.5 12.7 94 90 575 03/28/06 Lot 1 255 12 0 119.5 10.1 93 90 576 04/03/06 Lot 1 255 19 0 105.7 16.9 90 90 577 04/03/06 Lot 1 258 19 0 106.5 15.9 91 90 578 04/11/06 Lot 1 252 19 0 108.6 16.8 93 90 579 04/11/06 Lot! 252 19 0 105.7 17,4 90 90 636 07/23/08 Lot 1 257 24 0 112.6 12.8 91 90 637 07/23/08 Lot 1 260 18 0 105.3 14.5 91 90 FG 638 07/23/08 Lot 1 255 18 0 106.0 14.0 92 90 Project No. 06442-32-04A October 30, 2008 TABLE I EXPLANATION OF CODED TERMS - TEST SUFFIX A, B, C.... : Retest of previous density test failure, following moisture conditioning and/or recompaction. Fill in area of density test failure was removed and replaced with properly compacted fill soil. - PREFIX CODE DESIGNATION FOR TEST NUMBERS DTN - DUPLICATE TEST NUMBER FG - FINISH GRADE ST - SLOPE TEST - CURVE NO. Corresponds to curve numbers listed in the summary of laboratory maximum dry density and optimum moisture content test results table for selected fill soil samples encountered during testing and observation. - ROCK CORRECTION For density tests with rock percentage greater than zero, laboratory maximum dry density and optimum moisture content were adjusted for rock content. For tests with rock content equal to zero, laboratory maximum dry density and optimum moisture content values are unadjusted. SC: SandCone Test (ASTM D1556) NU: Nuclear Density Test (ASTM D2922) OT: Other - ELEVATION/DEPTH Test elevations/depths have been rounded to the nearest whole foot. - LOCATION DESCRIPTION (IP): Indicaes in-place tests. Where (IF) appears in the location description, the compaction procedures were not observed by a representative of Geocon. Tests were taken at the surface or in test pits after placement of the fill. The results of these tests are indicative of the relative compaction at the location of the test only and may not be extrapolated to adjacent areas. Geocon has no opinion regarding the relative compaction of fill in adjacent areas. Project No. 06442-32-04A October 30, 2008 TABLE II SUMMARY OF LABORATORY MAXIMUM DRY DENSITY AND OPTIMUM MOISTURE CONTENT TEST RESULTS ASTM D 1557 Proctor Curve No. Source and Description Maximum Dry Density (pct) Optimum Moisture Content (%) 1 Dark brown, Silty, fine SAND 129.2 8.5 2 Olive brown, Silty, fine to coarse SAND with trace gravel 130.1 8.6 3 Very dark brown, Clayey, fine to coarse SAND with trace gravel 128.0 8.9 4 Very dark brown, Clayey, fine to medium SAND with trace gravel 123.9 12.0 12 Olive gray, Silty, fine to medium SAND 128.9 9.2 13 Light yellowish brown, Silty, fine to coarse SAND with silt 122.0 11.8 15 Olive green, Silty CLAY 112.2 17.8 18 Light brown, fine, Sandy SILT 115.5 15.0 19 Dark brown, Clayey, fine to coarse SAND with trace gravel 117.0 14.7 24 Olive brown, Clayey, fine to coarse SAND with trace silt 124.0 11.3 TABLE III SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS ASTMD4829 Sample No. (Lot No.2 and location on Pad) Moisture Content (%) Dry Density (pci) Expansion Index Before Test After Test El-39(Southwest Portion) 9.4 20.7 112.7 50 EI-40 (Northwest Portion) 10.3 24.3 108.6 74 EI-41 (Northeast Portion) 8.9 1 20.8 112.8 56 EI-42 (Southeast Portion) 8.9 1 19.1 114.7 46 TABLE IV SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS CALIFORNIA TEST NO. 417 Sample No.* % Soluble Sulfate Sulfate Exposure Class** Exposure Rating EI-39 0.290 52 Severe (high risk) EI-40 0.183 Si Moderate (medium risk) EI-41 0.268 52 Severe (high risk) EI-42 0.216 S2 Severe (high risk) *See Table ifi for location on pad. **Reference: Table 4.2.1, ACT 318-08 report. Project No. 06442-32-04A October 30, 2008